There are many different types of universal joints used for transmission of rotational energy. One type of universal joint includes a telescoping constant velocity joint, sometimes referred to as a tripot universal joint. One application for telescoping constant velocity joints, such as various tripot joints, has been automotive axial drive shafts, particularly in front-wheel-drive vehicles between the transaxle differential and the driving wheel. The telescoping constant velocity joint transmits a torque at various rotational speeds, joint angles and telescopic positions between shaft members.
The telescoping constant velocity joint may include a first rotatable shaft member and a second rotatable shaft member. The first shaft member includes a housing. The housing defines a plurality, but preferably three, internal guide channels. The guide channels extend along and parallel to a longitudinal axis of the first shaft member. The second shaft member includes a spider disposed at one end of the second shaft member. The spider is disposed within the housing of the first shaft member. The spider includes a plurality, but preferably three, radially extending trunnions. The telescoping constant velocity joint includes a plurality of roller assemblies. One of the roller assemblies is rotatably mounted to each of the trunnions, and is disposed in one of the guide channels in rolling engagement with the guide channel. The roller assemblies generally include an inner ball disposed within an outer ball and separated by a plurality of roller bearings. The roller bearings are employed to reduce the friction between the outer surface of the inner ball and the inner surface of the outer ball by providing a rotatable assembly whose frictional losses are defined by the rolling friction between the roller bearings and these surfaces rather than sliding or rolling friction that would otherwise exist between these surfaces if the roller bearings were not employed. The roller bearing elements, in combination with the inner ball and the outer ball, effectively create a needle bearing assembly. Such assemblies are widely used in conjunction with tripot universal joints to reduce frictional losses and obtain the desired operational performance from these joint.
While roller bearing assemblies of the type described are capable of providing acceptably low frictional losses and joint operational performance, they are generally costly to manufacture and require design of the roller assemblies to accommodate the roller bearings, including the incorporation of components and design features needed to retain the bearings. Further, the incorporation of the bearings themselves requires that a suitable space envelope in the roller assembly be dedicated to them and any components needed to retain them. Therefore, it is desirable to provide roller assemblies having acceptable frictional losses and operational performance while also avoiding the limitations described above associated with the use of roller bearings to provide this performance.